This invention relates to an electronic musical instrument of a partials synthesis type wherein there are provided a predetermined number of partials wave computation time slots which are allotted for calculation of respective tone partial components including a fundamental wave (basic tone) and the harmonics thereof (overtones) which in combination constitute a musical tone and wherein respective components calculated by the time slots are multiplied with corresponding amplitude coefficients and the resulting products are synthesized to form a musical tone.
A typical electronic musical instrument of the partials (harmonics) synthesis type utilizing a digital technique is disclosed in U.S. Pat. No. 3,809,786. In this electronic musical instrument each one of W (number including fundamental) harmonic components are independently calculated in consecutive time slots or time intervals t.sub.c =t.sub.x /W, where t.sub.x represents an interval of calculating the amplitude value of a musical tone waveform at a sample point. Thus, each one of W harmonic wave computation time slots is made to correspond to a specific harmonic wave component. For instance, a first harmonic wave component is calculated in a first harmonic wave computation time slot t.sub.cl, a second harmonic wave component is calculated in a second harmonic wave computation time slot t.sub.c2 and so on, so that the Wth harmonic wave component is calculated in the Wth harmonic wave computation time slot. Accordingly, in a prior art electronic musical instrument of this type, in response to a depressed key, a musical tone comprising synthesized W harmonic wave components is always formed. In this case, the resulting musical tone is a tone of a single predetermined kind and of the tone pitch corresponding to the depressed key.
Generally, when playing musical instruments, an ensemble of a plurality of musical instruments has been conducted for the purpose of enhancing the effect of the performance.
However, with the prior art electronic instrument described above, a musical tone of only a single kind is generated for one depressed key so that it is impossible to obtain an ensemble performance. Especially, it has been impossible to simultaneously generate a plurality of musical tones having different pitches in response to one depressed key. With the prior art electronic musical instrument, if it is desired to provide an ensemble performance by simultaneously generating a plurality of musical tones having slightly different tone pitches and different tone colors in response to a single depressed key, it is necessary to provide a plurality of parallel-connected harmonic component computation channels or time slots described above. This not only complicates the circuit construction but also increases the cost of manufacturing.